Patients with AD showed a significant thickness reduction in global and temporal superior quadrants in pRNFL and in superior pericentral and peripheral sectors of RT. These findings may reflect a peripapillary and retinal changes characteristic of AD, suggesting the importance of SD-OCT as a potential adjuvant in early diagnosis of AD. Further studies are needed to understand which retinal layers and macular sectors are more useful as potential ocular biomarker over time in AD.

IntroductionThe purpose of this study was to measure and to compare macular choroidal thickness (CT) between patients with mild Alzheimer's disease (AD), patients without AD, and elderly patients.MethodsCT was measured manually in 13 locations at 500-μm intervals of a horizontal and a vertical section from the fovea. Linear regression models were used to analyze the data.ResultsFifty patients with a diagnosis of mild AD (73.1 years), 152 patients without AD (71.03 years), and 50 elderly without AD (82.14 years) were included. In the AD patients, CT was significantly thinner in all 13 locations (P < .001—comparing with age-match group), and comparing with the elderly group, a more pronounced difference was found in two locations temporal to the fovea.DiscussionPatients with AD showed a significant choroidal thinning even when compared with elderly subjects. The reduction of CT may aid in the diagnoses of AD, probably reflecting the importance of vascular factors in their pathogenesis.

Results indicate that the time of measurement after femtosecond affects the estimated flap thickness. Waiting 20 minutes after laser treatment permitted easier separation and may eliminate the effect of variable corneal dehydration on flap measurement by subtraction pachymetry.

The most relevant optical elements either do not have available measurement instruments or the existing instruments still need to improve their accuracy. Ray tracing can be used as an optical assessment technique, and may be the correct path for future personalized refractive assessment.